Question

State whether true or false.
A concave mirror is always used as a street light reflector.
A. True
B. False

Answer 1

Hint: A street light reflector is a device that reflects the rays of light falling on it. We all know that a mirror also reflects. Therefore, you can say that a street light reflector is just like a mirror. It is useful at night to see objects clearly.

Complete step by step answer:
A street light reflector is a device that reflects the rays of light falling on it. We all know that a mirror also reflects. Therefore, you can say that a street light reflector is just like a mirror.
We know that a street light reflector reflects the light falling on it. Let us now know the purpose of a street light reflector.
As the name suggests, street light reflectors are used on the streets. Due to the absence of sunlight, there is darkness while travelling on the road. We have headlights to our vehicles but a street light reflector is used to help us to see in all directions.
The mirror used in a street light reflector is a convex mirror. A convex mirror diverges the rays of light falling on it, in all the directions. That is why a convex mirror is also called a diverging mirror.
For example, if you see the given figure, the parallel rays of light fall on the convex mirror and they reflect and diverge away in such a way that they appear to be emerging from the focus (F) of the mirror.

This shows that a convex mirror diverges the light rays falling on it.
When the light of our vehicle's headlight falls on the reflector, the convex mirror diverges the light rays in all the directions thus lighting up the surrounding area. This makes us able to see much better at night.
We now know that the mirror used in a street light reflector is a convex mirror and not a concave mirror. Therefore, the given statement is false.
Hence, the correct option is B.

Note: Let us discuss the reason for not using a concave mirror in a street light reflector.
A concave mirror reflects the rays of light falling on it in such a way that the reflected rays converge at a single point. Hence, a concave mirror helps in focusing the light. However, we need the light rays to diverge in a street light reflector. Therefore, a concave mirror is not used in the reflector.
A concave mirror is also called a converging mirror.
This can be depicted in the form of a ray diagram as shown below. The rays of light in the diagram are parallel to each other. When the incident rays are parallel to the principal axis of the mirror, after reflection they intersect at the focus of the mirror.